Index: llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2134,15 +2134,11 @@
 
     if (!C) continue;
 
-    // Ignore negative constants, as the code below doesn't handle them
-    // correctly. TODO: Remove this restriction.
-    if (!C->getValue().isStrictlyPositive()) continue;
-
     /* Add new PHINode. */
     PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
 
     /* create new increment. '++d' in above example. */
-    Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
+    Constant *CFP = ConstantFP::get(DestTy, C->getSExtValue());
     BinaryOperator *NewIncr =
       BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
                                Instruction::FAdd : Instruction::FSub,
Index: llvm/test/CodeGen/X86/negative-stride-fptosi-user.ll
===================================================================
--- llvm/test/CodeGen/X86/negative-stride-fptosi-user.ll
+++ llvm/test/CodeGen/X86/negative-stride-fptosi-user.ll
@@ -9,27 +9,28 @@
 define void @foo(i32 %N) nounwind {
 ; CHECK-LABEL: foo:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    pushq %rbp
 ; CHECK-NEXT:    pushq %rbx
-; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    subq $16, %rsp
 ; CHECK-NEXT:    testl %edi, %edi
 ; CHECK-NEXT:    jns .LBB0_3
 ; CHECK-NEXT:  # %bb.1: # %bb.preheader
 ; CHECK-NEXT:    movl %edi, %ebx
-; CHECK-NEXT:    xorl %ebp, %ebp
+; CHECK-NEXT:    xorpd %xmm0, %xmm0
 ; CHECK-NEXT:    .p2align 4, 0x90
 ; CHECK-NEXT:  .LBB0_2: # %bb
 ; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
-; CHECK-NEXT:    xorps %xmm0, %xmm0
-; CHECK-NEXT:    cvtsi2sd %ebp, %xmm0
+; CHECK-NEXT:    movsd %xmm0, 8(%rsp)          # 8-byte Spill
+; CHECK-NEXT:    movsd 8(%rsp), %xmm0          # 8-byte Reload
+; CHECK-NEXT:    # xmm0 = mem[0],zero
 ; CHECK-NEXT:    callq bar
-; CHECK-NEXT:    decl %ebp
-; CHECK-NEXT:    cmpl %ebp, %ebx
+; CHECK-NEXT:    movsd 8(%rsp), %xmm0          # 8-byte Reload
+; CHECK-NEXT:    # xmm0 = mem[0],zero
+; CHECK-NEXT:    addsd .LCPI0_0(%rip), %xmm0
+; CHECK-NEXT:    incl %ebx
 ; CHECK-NEXT:    jne .LBB0_2
 ; CHECK-NEXT:  .LBB0_3: # %return
-; CHECK-NEXT:    addq $8, %rsp
+; CHECK-NEXT:    addq $16, %rsp
 ; CHECK-NEXT:    popq %rbx
-; CHECK-NEXT:    popq %rbp
 ; CHECK-NEXT:    retq
 entry:
   %0 = icmp slt i32 %N, 0                         ; <i1> [#uses=1]
Index: llvm/test/Transforms/LoopStrengthReduce/X86/2008-08-14-ShadowIV.ll
===================================================================
--- llvm/test/Transforms/LoopStrengthReduce/X86/2008-08-14-ShadowIV.ll
+++ llvm/test/Transforms/LoopStrengthReduce/X86/2008-08-14-ShadowIV.ll
@@ -208,6 +208,42 @@
   ret i32 %accum.next
 }
 
+; void negative_step(int n) {
+;   for (int i = 10; i > n; i += -1)
+;     foo((double)i);
+; }
+;
+; Transformed to:
+;
+; void negative_step(int n) {
+;   for (int i = 10, double d = 10.0; i > n; i += -1, d += -1.0)
+;     foo(d);
+; }
+
+define void @negative_step(i32 %n) {
+; CHECK-LABEL:  negative_step(
+; CHECK-NOT:          sitofp
+entry:
+  br label %while.header
+
+while.header:
+  %i = phi i32 [ 10, %entry ], [ %i.next, %latch ]
+  %cond = icmp sgt i32 %i, %n
+  br i1 %cond, label %body, label %exit
+
+body:
+  %cast = sitofp i32 %i to double
+  call void @foo(double %cast)
+  br label %latch
+
+latch:
+  %i.next = add nsw i32 %i, -1
+  br label %while.header
+
+exit:
+  ret void
+}
+
 declare void @bar(i32)
 
 declare void @foo(double)